Furfural is a chemical intermediate readily available from lignocellulosic biomass, and it is industrially produced since 1921 mainly from residues of agriculture. Furfural offers alternative ways for producing numerous materials as well as new generation biofuels. Potential and upcoming markets for furan resins cover a wide spectrum with massive potential utilization, from wood preservatives to construction materials. In the past furfural has been already used as starting material for the production of important chemical intermediates like THF. Favourable balances between oil prices and furfural availability, as well as green oriented policies, are likely to drive a switch back to the furfural based routes.
As far as the energy sector is concerned, direct hydrogenation derivatives of furfural also have a high potential as alternative liquid fuels and fuel extenders. 2-Methyltetrahydrofuran (MTHF) has been proven to show superior characteristics as fuel extender in regular gasoline, as well as in alternative fuels formulations based on ethanol (P-series fuels). 2-Methylfuran and tetrahydrofurfurylalcohol (THFA) could also be potential candidates as biomass derived octane enhancer, and as diesel fuel additive. Furthermore, by controlled reactions involving furfural, such as aldol condensation, alkylation and etherification, larger molecules may be obtained, that can undergo subsequent hydrogenation/hydrogenolysis to molecules with superior fuel characteristics, such as higher alkanes.
Current furfural production processes are energy intensive and costly. Moreover, they exhibit relatively low yields, 50-60% of the theoretical, and they are poorly integrated with processes aimed at valorising the entire biomass feedstock. This makes furfural less suitable for the fuel industry at the moment, and not always cost competitive with oil derivatives in the chemical industry. The development of novel production processes is needed in order to unlock the potential of this biomass derived platform chemical.
In WO 81/00407 (U.S. Pat. No. 4,366,322) a process for the production of furfural is described, wherein pentoses are converted into furfural at atmospheric pressure and a temperature below 110° C., in a strong acid medium (6N acid). This process shows a low yield and produces a large amount of byproducts. It also has a large energy requirement.
In DE 740602 the production of furfural has been described, using a recycle of part of the product stream to the bottom of the column. This process shows low yield and substantial by-product formation.
Traditional processes employ a large share of their primary energy input to produce high pressure steam to strip out furfural from the reacting system, and for its subsequent purification by distillation. The total energy consumption in such processes ranges from 15 to 50 ton of steam per ton of furfural produced. Nevertheless, the direct reduction of steam usage is usually detrimental for the furfural yield from biomass, and for this reason, despite the related energy costs, plentiful steam stripping is crucial in furfural production.